I would say to go for Monarchy and switch that as your government. Build lots of wonders and settle all your great people or they won't count towards a cultural victory. Remeber to keep your cities well defended. Once you get mathmatics, it will help to build catapult armies and attack with them from within your city on oncoming vanguards. It will lessen the inpact on your fortified archers/pikemen. Plus, after killing your attackers and you feel confident to go on the offense and attack with those same catapults :D